Recently, a receiving device that can receive a wireless signal transmitted from a satellite is equipped on a movable body, such as a vehicle, a mobile phone and the like. Global positioning system (GPS) positioning enables estimation of the position of the movable body equipped with this type of receiving device. A position estimation technology that uses this type of receiving device is a common basic technology that is important in a variety of fields including navigation, security, entertainment and the like.
Further, a position estimation method is also conceivable in which a wireless terminal that performs wireless communication with a base station (an access point) of a wireless local area network (LAN) measures a signal intensity of a signal transmitted from the wireless base station, and a position estimation device that can communicate with the wireless terminal estimates the position of the wireless terminal based on the signal intensity. For example, the wireless LAN base station transmits a beacon at a constant frequency (for example, five times per second) to notify a surrounding area of the existence of the wireless LAN base station. The wireless terminal transmits the signal intensity of the beacon to the position estimation device. The position estimation device can estimate the position of the wireless terminal based on the signal intensity and the position of the wireless LAN base station that is registered in advance. With the above-described position estimation method, the wireless LAN base station is provided also in indoor or underground environments. Therefore, it is possible to perform position estimation in indoor or underground environments, which is difficult using the position estimation technology based on the GPS positioning.
In this type of position estimation method, when a user carrying a wireless terminal is present in a building or structure, not only the latitude and longitude of the wireless terminal, but also information indicating which floor of the building or structure the user is currently on is important. For example, Patent Document 1 discloses a technology in which a wireless terminal measures signal intensities of wireless signals transmitted from a plurality of base stations, and a position estimation server estimates that the wireless terminal exists on the floor of a base station that is a transmission source of a wireless signal with a strong signal intensity.